Fluid pressure regulating and control device

ABSTRACT

A controlled leakage device is provided which can control the flow of fluid out of a chamber over a wide range of fluid conditions, i.e., from subcooled liquid to superheated vapors. A hydrostatic balancing system is utilized to cause the seating force on a pressure barrier member to be related to the lifting force on the barrier member. Thus, the device can be constructed to remain in balance over the large change in lifting force that results when the fluid changes phase. Possible applications for the device include safety and relief valves for pressurizers, steam generators and boilers, and shaft seals.

United States Patent 1 Andrews et a1.

[ lMarch 13, 1973 1 1 FLUID PRESSURE REGULATlNG AND CONTROL DEVICE [73]Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

221 Filed: Oct.27, 1971 21 Appl.No.: 193,114

52 u.s.c| ..137/1s4,137/494 [51] lnt.Cl ..Fl6k33/36 [58] Field ofSearch....l37/l83, 200, 494, 484, 484.2

[56] References Cited UNITED STATES PATENTS Mueller ..l37/l83 3,347,55210/1967 Frisch ..277/27 Primary Examiner-Alan Cohan Attorney-A. T.Stratton et a1.

[57] ABSTRACT A controlled leakage device is provided which can controlthe flow of fluid out of a chamber over a wide range of fluidconditions, i.e., from subcooled liquid to superheated vapors. Ahydrostatic balancing system is utilized to cause the seating force on apressure barrier member to be related to the lifting force on thebarrier member. Thus, the device can be constructed to remain in balanceover the large change in lifting force that results when the fluidchanges phase. Possible applications for the device include safety andrelief valves for pressurizers, steam generators and boilers, and shaftseals.

20 Claims, 7 Drawing Figures PATENTEUHARI elm 3,720,222

' SHEET 2 OF 3 SYSTEM H4 fi I7 Hl 36 l" 3 I I INJECTION WATER -LOCATIONOF TAPER CIRCLE 35 a AREA I[[\ l,

SPRING FORCE 1 lNCREASED GAP g NORMAL 1 GAP i l AREA 11 CATION OFPASSAGEWAY o FIG.3

SHEET 3 BF 3 SUB- COOLED LIQUID PATENTEUNARI 31973 TWO-PHASE 2%? FlG.4

NORMAL PRESSURE LLOCATION OF PASSAGEWAY D OVE R PRES FLUID FLUIDPRESSURE REGULATING AND CONTROL DEVICE BACKGROUND OF THE INVENTION Thisinvention relates, generally to fluid pressure regulating and controldevices and, more particularly to high pressure fluid control devices ofthe controlled leak age-type.

Heretofore, the control of system pressure increases in power generatingplants has been accomplished by utilizing sprays, relief valves andsafety valves. The sprays are constructed to control pressure changesdue to small load changes; the relief and safety valves to controlpressure during accident conditions. Prior relief and safety valves havebeen less reliable in service than desirable due to problems such assimmering and the resulting wire drawing (channeled erosion), due tosteam leakage. The pressure bands required to alleviate simmeringproblems contribute to the necessity of setting the operating pressureof a pressurized vessel, such as a nuclear reactor, at a value that issignificantly lower than the design pressure of the vessel. Thefollowing table shows the various pressure levels required with priorcontrol devices and those made possible with the device hereindisclosed:

TABLE 1 PRIOR SAR 2575 All Safety 2575 Valve fully valves open open 25502550 Safety Valve 2525 2525 Action 2500 1st Safety Design 2500 ReactorTrip valve opens Pressure Relief 2475 2475 Action 2450 2450 Valve startsto open 2425 2425 Nominal Operating Pressure 2400 Reactor Trip 2400 23752375 2350 Relief valves 2350 open 2325 Sprays fully on 2325 2300 23002275 Sprays on 2275 2250 Nominal 2250 Operating Pressure As shown byTable l, the device herein disclosed can be constructed to perform thefunctions of both the relief and safety valves over a smaller pressureband than is required with prior devices, thereby permitting increasingreactor operating pressure with no increase in design pressure. In atypical reactor the nominal operating pressure can be raised from 2250psi to 2425 psi. Thus, the reactor can operate at a higher temperaturewhich greatly improves its efficiency.

In order to make the above improvements possible, it was necessary toprovide a fluid pressure regulating and control device havingconfronting faces that can adequately restrict fluid flow with water orsteam in the interface passage between the confronting faces of thedevice.

SUMMARY OF THE INVENTION In accordance with the present invention, acontrolled leakage face-type device is provided to control the flow of afluid from a high pressure region to a low pressure region. An annularbarrier member or ring is movably mounted in a housing having a facetherein confronting a face on the ring. A hydrostatic balancing systemis utilized to control the leak rate through the interface passagebetween the confronting faces under various operating conditions. Thispermits a small stable leakage to be maintained in the closed" positionso that the use of injection water and/or cold loop concepts arefeasible to control the temperature and particulate content of theeffluent. The hydrostatic balancing system includes a variable seatingforce whose magnitude depends on the fluid conditions between the faces.Thus, the device is constructed to remain in balance over the largechange in lifting forces that results when the fluid changes phase.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of thenature of the invention, reference may be had to the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. I is a view, partly in section and partly in elevation, of a fluidpressure regulating and control device embodying principal features ofthe invention;

FIG. 2 is a diagrammatic view, in section, of the device shown in FIG. 1with slight modifications;

FIGS. 3, 4 and 5 are force diagrams graphically illustrating the forcesacting on the device during its operation under different conditions;

FIG. 6 is a hydraulic force diagram illustrating the forces acting onthe device when it is under a balanced condition; and

FIG. 7 is a diagrammatic view illustrating the use of the device in apower system which includes a pressurizer and a cold leg or loop heatexchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENT As used herein, the term fluidincludes a liquid, a vapor, or a gas. In FIG. 1 of the drawings there isshown a fluid pressure regulating and control device or valve 10 whichis suitable for use with a vessel, such as a boiler, or a steamgenerator, or a pressurizer for a pressurized liquid cooled nuclearreactor, containing a twophase fluid, such as water, under pressure. Asexplained more fully hereinafter, the device 10 may be utilized as acombination safety and relief valve for the vessel, thereby making itunnecessary to supply two separate valves as previously required.

The valve 10 comprises housing members H1, H2, H3 and H4 which define ahigh pressure fluid chamber HP and a low pressure fluid chamber LP. Thehousing member Hl has an inlet opening 12 therein through which hightemperature, high pressure fluid enters the valve, and the housingmember H4 has an outlet opening 13 therein from which low pressure fluidleaves the valve. The member H4 spaces the members HI and H2 and issecured to them by means of stud bolts 14. The member H3 is clampedbetween the member H2 and H4 by the bolts 14. Metal O-ring seals 15 areprovided in the joints between the housing members. A bleeder passageway16 is provided in the member H3 to bleed off any fluid that might leadpast the first O-ring seal between the members H2 and H3.

In order to permit a controlled amount of leakage fluid to flow from thehigh pressure chamber HP into the low pressure chamber LP, ahydrostatically balanced annular barrier member or valve ring B ismovably mounted within the housing members. The housing member H1 has anannular face 17 thereon confronting the valve ring face 18. As shownmore clearly in FIG. 2, an interface passage 19 extends between theconfronting faces 17 and 18 for the flow of the leakage fluid. Spacedbellows 21 and 22 extend between the valve ring B and the housing memberH3 to complete the barrier between the high pressure chamber HP and thelow pressure chamber LP. The bellows are secured to the valve ring B andthe housing member H3, as by welding, and permit vertical movement ofthe valve ring, under the influence of unbalanced forces.

As well known in the art, the leakage fluid flowing through theinterface passage 19 exerts a lifting force on the valve ring B. Thislifting force is partly balanced by providing a face 23 on the valvering B, opposite the confronting face, which is exposed to the highpressure fluid in the chamber HP. A seating force is also provided byone or more relatively strong springs mounted in a container 24 seatedin the valve ring B. The force of the balancing springs 5, acting on thevalve, is adjustable within certain limits by means of a set screw 25bearing on a retainer 26 vertically movable in a sleeve 27 secured tothe housing member H2, as by welding. Rotation of the retainer 26 isprevented by a pin 28 slidably disposed in a slot 29 in the sleeve 27.The set screw 25 is sealed from the atmosphere during normal operationby a bolted enclosure cap 30 with a metal O-ring seal 31.

In order to provide a variable seating force on the valve ring whosemagnitude depends on the fluid conditions in the passage between theconfronting faces, a feedback chamber FB is provided between the bellows21 and 22 which function as seal means cooperating with the valve ringand the housing members to define the feedback chamber. A passageway Dextends through the valve ring B to permit fluid to flow from theinterface passage 19 into the feedback chamber FB. Additionalpassageways D may be provided if desired. A face 32 is provided on thevalve ring B which is exposed to the pressure of the fluid in thefeedback chamber FB. In this manner, the device is constructed to remainin balance over the large change in lifting forces that results when thefluid changes phase or state, as from water to steam.

As described in U.S. Pat. No. 3,347,552, issued Oct. 17, 1967 to ErlingFrisch and assigned to Westinghouse Electric Corporation, in order toobtain a self-restoration of the relative position of the valve ring Band the housing member H1 upon a variation in the valve gap caused byvibration, a fluid flow path of decreasing thickness is provided fromthe high pressure edge or extremity 33 (FIG. 2) to a position betweenthe valve face extremities 33 and 34. More specifically, as shown inFIG. 2, the fluid flow path of decreasing thickness extends between theedge 33 and an intermediate concentric circle located at 35. Thedecreasing flow path thickness may be formed by tapering the confrontingsurface 18 of the valve ring slightly away from the confronting surface17 of the housing member H1 between the circle 35 and the edge 33 of thevalve ring B. The angle of the taper shown on the drawing isexaggerated.

As explained hereinbefore, the seating force on the valve ring isaugmented by a force which is proportional to the interface pressure ata selected point of the flow path. As shown, the entrance to thepassageway D is so located between the concentric circle 35 and the lowpressure edge 34 of the valve ring as to obtain the desired operatingcharacteristics of the valve.

The use of hydrostatic balancing to control the leak rate under thevarious operating conditions permits a small stable leakage to bemaintained in the closed position of the valve. Thus, injection waterand/or a cold loop concept may be utilized to control the temperatureand the particulate content of the effluent. As shown in FIGS. 1 and 2,a passageway 36 is provided in the housing member H1 to inject waterinto the interface passage 19 at a pressure slightly higher than thenormal operating pressure in the high pressure chamber HP. Adistribution cavity 37 is provided for the injection water which exitsout of the valve and into the circulatory system in which the valve isconnected. The injection water may be supplied from a suitable source(not shown). An orifice 38 is provided in the injection water line tolimit the flow rate of the injection water. The distribution cavity 37for the injection water is located between the entrance to thepassageway D into the feedback chamber and the high pressure extremityof the interface passage, preferably relatively close to the highpressure extremity. Thus, most of the injection water flows through theinterface passage into the low pressure chamber.

A bushing 39, which is attached to the valve ring B by threading, servesas a stop to limit upward movement of the valve ring, thereby limitingthe maximum valve opening. Another bushing 40, which is bolted to thehousing member H3, overlaps the bushing 39 and serves as a guide for thevalve ring to keep it centered and to prevent radial motion of the valvering when it is lifted from its seat.

The operation of the valve may be better understood by referring toFIGS. 2 and 3. In the structure shown diagrammatically in FIG. 2, O-ringseals 41 and 42 are substituted for the bellows 21 and 22. Also, housingmembers H1 and H3 are combined into one member H2. The O-ring seals 41and 42 cooperate with the valve ring 8 and the housing member H2 todefine the feedback chamber FB.

NORMAL OPERATION In normal operation, (i.e., the closed" position) coolinjection water at a pressure slightly higher than P1 is injected intovalve interface from cavity 37, exiting into low pressure chamber LP.Since the pressure in cavity 37 is slightly higher than normal P1, asmall amount flows into high pressure chamber HP. This injection waterserves the following purposes:

1. Under normal conditions, it allows clean water to flow in the valveinterface, minimizing crude problems.

2. It allows for the normal collection of clean, uncontaminated water.

3. If prevents steam from forming in the interface when the valve isoperating normally.

The axial forces acting on the valve ring B in this equilibrium positionare depicted in FIG. 3. The solid lines are seating forces, the dashedlines are lifting forces. FIG. 2, which is a sketch of the valve crosssection, is shown above the force diagram to relate the pressure areasto their respective valve surfaces. The spring force (mechanical) isrepresented by an equivalent pressure area to facilitate demonstrationof balanced forces.

When the areas under the dashed line and the solid lines are equal, thevalve is in equilibrium at this separation. Furthermore, the equilibriumis stable since a deviation from this face separation results in a forceunbalance that tends to restore the valve ring to the equilibriumposition. For example, if the face separation is increased, the taper inthe interface flow path causes a decrease in the concavity of thelifting pressure distribution. The resulting decrease in lifting force(Area I, FIG. 3) is greater than the decrease in seating force (AreaII-Area III) so that a net seating force is developed. The net seatingforce is due primarily to the decreased pressure in the feedback chamberFB as the spring force is only slightly increased during this actionbecause very small displacements of the valve ring B occur. Similararguments apply when the face separation is decreased. Thus, a low,controllable leak rate is possible in this position.

HIGH PRESSURE OPERATION When the system pressure Pl attains a valuegreater than the injection pressure, system fluid begins to mix withinjection water and flow out of the valve. This eventually causes theaverage fluid temperature at the outlet to be higher than the boilingpoint of the fluid. Depending on the temperature and pressure of thefluid entering the valve and the particular valve construction,equilibrium is achieved with flashing occurring at the outlet, at someposition along the face, or (with steam as the sealed fluid) with steamover the entire interface. The pressure distribution that would occurwith flashing in the interface is illustrated schematically in FIG. 4.The orifice provided in the injection water line limits the flow rate ofinjection water during this condition. The greatly increased liftingforce, due to flashing, is offset by the increased seating force as aresult of communication of the feedback chamber P3 with the interfacethrough passageway D, thereby exposing part of the top surface of thevalve ring to the higher pressure in the interface passage and in thefeedback chamber.

When operating in the high pressure condition, the face separation and,consequently, the bypass flow is a function of system pressure if thisexceeds the injection pressure P. This is best understood by referringto the hydraulic force diagram, FIG. 6. The valve ring B is balanced bythe spring force Fsp and the hydraulic pressure forces when:

Fsp+P,A,+P A;,=P A (i) where P, is the mean pressure under the valvering (Area A,) and P, and P are the pressures acting on areas A and Arespectively, tending to seat the valve ring. Since the pressure on areaA is the low outlet pressure it has no effect on the balance of thevalve ring.

Equation (1) may also be written:

F,,,=P,A,(P,A,+P,A )=LFSF (2) where LF is the total hydraulic liftingforce and SF is the total hydraulic seating force.

Assuming now that the system pressure is increased by a factor X, thevalues of P and P; will also increase in approximately the sameproportion and Equation (2) may be written:

XP A X(P,A,+P A )=X(LFSF) a) This says that the difference betweenhydraulic lifting and seating forces is increased by the factor X,thereby upsetting the balance of the valve ring. As a result, the valvering will be forced away from its seat and compress the spring untilequilibrium again is attained when the spring force reaches a value ofXF,,,. This may be expressed by:

(5) where 8 is the valve ring separation and K is the spring constant.This shows that the valve ring separation increases with the increase ininlet pressure and is a function of the spring constant.

A valve construction is also possible using a cold loop instead ofinjection water. As shown diagrammatically in FIG. 7, the valve 10 isconnected to a pressure vessel P by means of a fluid conductor C havinga cold loop CL disposed in a heat exchanger HX having an inlet I and anoutlet 0. Cold water is circulated through the heat exchanger from asuitable source (not shown). Thus, the fluid flowing through the loop CLis subjected to the cooling effect of the heat exchanger. The vessel Pmay be a pressurizer for a reactor power system or any vessel containinga two-phase fluid under pressure.

The pressure balance of a valve of this type is depicted in FIG. 5. Theoperation of the valve is similar to that described above except thatthe valve is sensitive to changing inlet pressures over the range ofoperation. If the system pressure increases above the normal value, theface separation and flow rate increase as explained hereinbefore. Forsmall increases, the changes are shown by the cross-hatched areas inFIG. 5. Any increase in lifting force is balanced by an increase inseating force. As the pressure, and thus flow increase, the fluidtemperature increases. Since the rate of heat removal of the cold loopis relatively constant, this finally results in boiling and a newequilibrium is established as discussed previously.

The device herein disclosed can also be used as a seal which can controlleakage even if the fluid being handled increases significantly intemperature causing steam outflow. Thus, the device may be used toimprove the seals utilized on main coolant pumps.

From the foregoing description, it is apparent that the inventionprovides a fluid pressure regulating and control device which hasnumerous advantages over prior devices. When applied to the problem ofreactor pressure control, simmering and associated problems areeliminated because a continuous controlled leakage flow through thedevice is maintained.

As shown by Table l, the device can be constructed to perform thefunctions of both the relief and safety valves over a smaller pressureban than is required with prior valves, thereby permitting increasingreactor operating pressure with no increase in design pressure. Thus,the efficiency of a reactor can be improved to realize a saving in thecost of operating a power generating plant. The present device can beeconomically manufactured and installed.

We claim as our invention:

1. A fluid pressure regulating and control device, comprising housingmembers defining a high pressure fluid chamber and a low pressure fluidchamber, an annular barrier member movably mounted within the housingmembers to permit a controlled amount of leakage fluid to flow from thehigh pressure chamber into the low pressure chamber, an annular face inthe housing, a face on the barrier member confronting the face in thehousing with an interface passage therebetween for the flow of theleakage fluid, said leakage fluid exerting a lifting force on thebarrier member, a face on the barrier member opposite the confrontingface and exposed to the high pressure fluid to provide a seating forceon the barrier member, seal means cooperating with the barrier memberand the housing members to define a feedback pressure chamber, saidbarrier member having a passageway therethrough permitting fluid to flowfrom the interface passage into the feedback pressure chamber, and saidbarrier member having an additional face thereon exposed to the pressureof the fluid in the feedback chamber to provide a variable seating forceon the barrier member having a magnitude depending on fluid conditionsin the interface passage.

2. The device defined in claim 1, including spring means also providinga seating force on the barrier member.

3. The device defined in claim 1, including means for injecting a liquidinto the interface passage at a pressure higher than the normaloperating pressure in the high pressure chamber.

4. The device defined in claim 3, wherein the liquid is injected intothe interface passage at a point between the high pressure extremity ofthe interface passage and the passageway which permits fluid to flowfrom the interface passage into the feedback pressure chamber.

5. The device defined in claim 1, wherein the confronting face on thebarrier member is tapered to provide a fluid flow path of decreasingthickness from the high pressure edge of the barrier member to aconcentric circle intermediate the high pressure edge of the barriermember and the low pressure edge of the barrier member.

6. The device defined in claim 5, wherein the entrance to the passagewaypermitting fluid to flow from the interface passage into the feedbackpressure chamber is located between said concentric circle and the lowpressure edge of the barrier member.

7. The device defined in claim 1, wherein the seal means comprisesbellows extending between the barrier member and a housing member.

8. The device defined in claim 1, including a first bushing threadedlyattached to the barrier member and cooperating with a housing member tolimit the movement of the barrier member.

9. The device defined in claim 8, including a second bushing attached tothe housing member and cooperating with the first bushing to guide themovement of the barrier member.

10. The device defined in claim 1, wherein one of the housing membershas a high pressure inlet opening therein, another member has a lowpressure exit opening therein and is secured to and spaces the otherhousing members.

I]. A fluid pressure regulating and control valve for use with a vesselcontaining a two-phase fluid under pressure, said valve comprisinghousing members defining a high pressure fluid chamber and a lowpressure fluid chamber, a hydrostatically balanced valve ring movablymounted within the housing members to permit a controlled amount ofleakage fluid to flow from the high pressure chamber into the lowpressure chamber, an annular face on one of the housing members, a faceon the valve ring confronting the face on the housing member with aninterface passage therebetween for the flow of the leakage fluid, saidleakage fluid exerting a lifting force on the valve ring, a face on thevalve ring opposite the confronting face and exposed to the highpressure fluid to provide a seating force on the valve ring, seal meanscooperating with the valve ring and the housing members to define afeedback pressure chamber, said valve ring having a passagewaytherethrough permitting fluid to flow from the interface passage intothe feedback pressure chamber, said valve ring having an additional facethereon exposed to the pressure of the fluid in the feedback chamber toprovide a variable seating force on the valve ring having a magnitudedepending on fluid conditions in the interface passage, a fluidconductor connecting the vessel to the valve, and heat exchanger meansfor cooling the fluid flowing through the conductor.

12. The subject matter defined in claim 11, wherein the conductorincludes a loop subjected to the cooling effect of the heat exchangermeans.

13. The subject matter defined in claim 11, including spring means alsoproviding a seating force on the valve ring.

14. The subject matter defined in claim 11, wherein the confronting faceon the valve ring is tapered to provide a fluid flow path of decreasingthickness from the high pressure edge of the valve ring to a concentriccircle intermediate the high pressure edge of the valve ring and the lowpressure edge of the valve ring.

15. The subject matter defined in claim 11, wherein the entrance to thepassageway permitting fluid to flow from the interface passage into thefeedback pressure chamber is located between said concentric circle andthe low pressure edge of the valve ring.

16. A fluid pressure regulating and control valve, comprising housingmembers defining a high pressure fluid chamber and a low pressure fluidchamber, a valve ring movably mounted within the housing members topermit a controlled amount of leakage fluid to flow from the highpressure chamber into the low pressure chamber, an annular face on oneof the housing members, a face on the valve ring confronting the face onthe housing member with an interface passage therebetween for the flowof the leakage fluid, said leakage fluid exerting a lifting force on thevalve ring, a face on the valve ring opposite the confronting face andexposed to the high pressure fluid to provide a seating force on thevalve ring, seal means cooperating with the valve ring and the housingmembers to define a feedback pressure chamber, passageway meanspermitting fluid to flow from the interface passage into the feedbackpressure chamber, and an additional face on the valve ring exposed tothe pressure of the fluid in the feedback pressure chamber to provide avariable seating force on the valve ring having a magnitude dependtheextremities of the interface passage. ing on fluid conditions in theinterface passage. 19. The valve defined in claim 18, wherein the 17.The valve defined in claim 16, including spring passageway means extendsthrough the valve ring. means also providing a seating force on thevalve ring. 20. The valve defined in f" including means 18. The valvedefined in claim 16, wherein the enforadiustmgthe force Ofthe Sprmgmeans trance to the passageway means is located intermediate

1. A fluid pressure regulating and control device, comprising housingmembers defining a high pressure fluid chamber and a low pressure fluidchamber, an annular barrier member movably mounted within the housingmembers to permit a controlled amount of leakage fluid to flow from thehigh pressure chamber into the low pressure chamber, an annular face inthe housing, a face on the barrier member confronting the face in thehousing with an interface passage therebetween for the flow of theleakage fluid, said leakage fluid exerting a lifting force on thebarrier member, a face on the barrier member opposite the confrontingface and exposed to the high pressure fluid to provide a seating forceon the barrier member, seal means cooperating with the barrier memberand the housing members to define a feedback pressure chamber, saidbarrier member having a passageway therethrough permitting fluid to flowfrom the interface passage into the feedback pressure chamber, and saidbarrier member having an additional face thereon exposed to the pressureof the fluid in the feedback chamber to provide a variable seating forceon the barrier member having a magnitude depending on fluid conditionsin the interface passage.
 1. A fluid pressure regulating and controldevice, comprising housing members defining a high pressure fluidchamber and a low pressure fluid chamber, an annular barrier membermovably mounted within the housing members to permit a controlled amountof leakage fluid to flow from the high pressure chamber into the lowpressure chamber, an annular face in the housing, a face on the barriermember confronting the face in the housing with an interface passagetherebetween for the flow of the leakage fluid, said leakage fluidexerting a lifting force on the barrier member, a face on the barriermember opposite the confronting face and exposed to the high pressurefluid to provide a seating force on the barrier member, seal meanscooperating with the barrier member and the housing members to define afeedback pressure chamber, said barrier member having a passagewaytherethrough permitting fluid to flow from the interface passage intothe feedback pressure chamber, and said barrier member having anadditional face thereon exposed to the pressure of the fluid in thefeedback chamber to provide a variable seating force on the barriermember having a magnitude depending on fluid conditions in the interfacepassage.
 2. The device defined in claim 1, including spring means alsoproviding a seating force on the barrier member.
 3. The device definedin claim 1, including means for injecting a liquid into the interfacepassage at a pressure higher than the normal operating pressure in thehigh pressure chamber.
 4. The device defined in claim 3, wherein theliquid is injected into the interface passage at a point between thehigh pressure extremity of the interface passage and the passagewaywhich permits fluid to flow from the interface passage into the feedbackpressure chamber.
 5. The device defined in claim 1, wherein theconfronting face on the barrier member is tapered to provide a fluidflow path of decreasing thickness from the high pressure edge of thebarrier member to a concentric circle intermediate the high pressureedge of the barrier member and the low pressure edge of the barriermember.
 6. The device defined in claim 5, wherein the entrance to thepassageway permitting fluid to flow from the interface passage into thefeedback pressure chamber is located between said concentric circle andthe low pressure edge of the barrier member.
 7. The device defined inclaim 1, wherein the seal means comprises bellows extending between thebarrier member and a housing member.
 8. The device defined in claim 1,including a first bushing threadedly attached to the barrier member andcooperating with a housing member to limit the movement of the barriermember.
 9. The device defined in claim 8, incluDing a second bushingattached to the housing member and cooperating with the first bushing toguide the movement of the barrier member.
 10. The device defined inclaim 1, wherein one of the housing members has a high pressure inletopening therein, another member has a low pressure exit opening thereinand is secured to and spaces the other housing members.
 11. A fluidpressure regulating and control valve for use with a vessel containing atwo-phase fluid under pressure, said valve comprising housing membersdefining a high pressure fluid chamber and a low pressure fluid chamber,a hydrostatically balanced valve ring movably mounted within the housingmembers to permit a controlled amount of leakage fluid to flow from thehigh pressure chamber into the low pressure chamber, an annular face onone of the housing members, a face on the valve ring confronting theface on the housing member with an interface passage therebetween forthe flow of the leakage fluid, said leakage fluid exerting a liftingforce on the valve ring, a face on the valve ring opposite theconfronting face and exposed to the high pressure fluid to provide aseating force on the valve ring, seal means cooperating with the valvering and the housing members to define a feedback pressure chamber, saidvalve ring having a passageway therethrough permitting fluid to flowfrom the interface passage into the feedback pressure chamber, saidvalve ring having an additional face thereon exposed to the pressure ofthe fluid in the feedback chamber to provide a variable seating force onthe valve ring having a magnitude depending on fluid conditions in theinterface passage, a fluid conductor connecting the vessel to the valve,and heat exchanger means for cooling the fluid flowing through theconductor.
 12. The subject matter defined in claim 11, wherein theconductor includes a loop subjected to the cooling effect of the heatexchanger means.
 13. The subject matter defined in claim 11, includingspring means also providing a seating force on the valve ring.
 14. Thesubject matter defined in claim 11, wherein the confronting face on thevalve ring is tapered to provide a fluid flow path of decreasingthickness from the high pressure edge of the valve ring to a concentriccircle intermediate the high pressure edge of the valve ring and the lowpressure edge of the valve ring.
 15. The subject matter defined in claim11, wherein the entrance to the passageway permitting fluid to flow fromthe interface passage into the feedback pressure chamber is locatedbetween said concentric circle and the low pressure edge of the valvering.
 16. A fluid pressure regulating and control valve, comprisinghousing members defining a high pressure fluid chamber and a lowpressure fluid chamber, a valve ring movably mounted within the housingmembers to permit a controlled amount of leakage fluid to flow from thehigh pressure chamber into the low pressure chamber, an annular face onone of the housing members, a face on the valve ring confronting theface on the housing member with an interface passage therebetween forthe flow of the leakage fluid, said leakage fluid exerting a liftingforce on the valve ring, a face on the valve ring opposite theconfronting face and exposed to the high pressure fluid to provide aseating force on the valve ring, seal means cooperating with the valvering and the housing members to define a feedback pressure chamber,passageway means permitting fluid to flow from the interface passageinto the feedback pressure chamber, and an additional face on the valvering exposed to the pressure of the fluid in the feedback pressurechamber to provide a variable seating force on the valve ring having amagnitude depending on fluid conditions in the interface passage. 17.The valve defined in claim 16, including spring means also providing aseating force on the valve ring.
 18. The valve defined in claim 16,wherein the entrance to the passageway means is located intermediate theextreMities of the interface passage.
 19. The valve defined in claim 18,wherein the passageway means extends through the valve ring.